Damper and washing machine having the damper

ABSTRACT

A damper includes a cylinder; a piston rod disposed to be movable linearly in the cylinder; a friction unit disposed to be movable in a radial direction inside the cylinder and generating a damping force by rubbing on an inner circumferential surface of the cylinder; and a damping force control unit mounted at the piston rod and controlling a damping force by moving the friction unit in the radial direction. A desired damping force is generated at a desired point such that a strong damping force can be generated at an interval where excessive vibration is generated and zero or a weak damping force can be generated at a normal interval, to thereby reduce vibration and noise of a washing machine.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates a damper of a washing machine and, more particularly, to a damper for reducing vibration and noise of a washing machine by generating a strong damping force at an interval where vibration is excessively generated and generating zero or a weak damping force at an interval where vibration is small.

2. Description of the Background Art

FIG. 1 is a sectional view of a general drum washing machine.

The related art drum washing machine includes a cabinet 2 forming the exterior, a tub 4 disposed inside the cabinet 2 and storing washing water, a drum 6 rotatably disposed at the inner side of the tub 4 and washing and dewatering the laundry, and a driving motor 10 positioned at a rear side of the tub 4 and rotating the drum 6 by being connected with the drum 6 by a driving shaft 8.

An inlet 12 allowing the laundry to be taken in or taken out therethrough is formed at a front side of the cabinet 2, and a door 14 for opening/closing the inlet 12 is provided at a front side of the inlet 12.

The tub 4 communicates with the inlet 12 of the cabinet 2, a plurality of support springs 16 are installed between an upper portion of the tub 4 and an upper inner wall of the cabinet 2, a plurality of dampers 18 are installed between a lower portion of the tub 4 and a lower inner wall of the cabinet 2 so as to reduce transfer of vibration generated from the tub 4 to the cabinet 2.

FIG. 2 is a sectional view showing the damper of the related art washing machine.

The damper 18 of the related art washing machine includes a cylinder mounted on the tub 4, a piston 22 inserted to be linearly moved in the cylinder 20, a piston rod 24 integrally formed with the piston 22 and connected with a bottom surface of the cabinet 2, and a friction member 26 fixed at an outer circumferential surface of the piston 22 and perform a damping operation while rubbing on an inner circumferential surface of the cylinder 20.

A hinge connection part 28 is formed at an upper end of the cylinder 20 and hinge-coupled with an outer circumferential surface of the tub 4. A lower end of the cylinder 20 is opened to allow the piston rod 24 to be inserted therethrough.

The piston 22 includes an insertion recess 32 formed on its outer circumferential surface, to which the friction member 26 is insertedly fixed. A hinge connection part 30 is formed at the lower end of the piston rod 24 and hinged at the bottom surface of the cabinet 2.

In the related art washing machine, when vibration is generated from the tub 4, the damper 18 rubs on the inner circumferential surface of the cylinder 20 to generate a damping force to reduce vibration.

However, the damper is disadvantageous in that the friction member 26 fixed at the piston 22 has such a single damping force that the same damping force is applied to the tub 6 at an interval, such as dewatering process period, where vibration is excessively generated and at an interval, such as a washing process period, where the washing machine is normally operated, the tub support capability and vibration attenuation capability are degraded.

Namely, if the frictional force generated from the friction member 26 is set strong, when small vibration is generated, the friction member 26 does not rub on the inner circumferential surface of the cylinder 20, resulting in that a damping force is not generated, so vibration of the tub 6 is transferred as it is to the cabinet 2 to increase noise and vibration of the washing machine.

If the frictional force generated from the friction member 26 is set weak, when strong vibration is generated, a damping force of the friction member 26 is reduced, failing to effectively support the tub 6, which results in degradation of performance of the washing machine and causing generation of more vibration.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a damper capable of controlling a damping force to generate a desired damping force at a desired point so that a strong damping force can be generated at an interval where excessive vibration is generated and zero or a weak damping force can be generated at a normal interval to thereby reduce vibration and noise of a washing machine, and the washing machine having the damper.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a damper including: a cylinder; a piston rod disposed to be movable linearly in the cylinder; a friction unit disposed to be movable in a radial direction inside the cylinder and generating a damping force by rubbing on an inner circumferential surface of the cylinder; and a damping force control unit mounted at the piston rod and controlling a damping force by moving the friction unit in the radial direction.

The friction unit includes: holders disposed at equal intervals in a circumferential direction inside the cylinder; a friction member fixed at an outer circumferential surface of the holders and rubbed on the inner circumferential surface of the cylinder according to radial movement of the holders; and an elastic member connected between holders and providing an elastic force in a direction that a radius of the holders is diminished.

The damping force control unit includes: an operation unit disposed at an inner circumferential surface of the holders and pressing the holders so as to be expanded in a radial direction; and a driving force generating unit mounted at an upper end of the piston rod and driving the operating unit.

To achieve the above object, there is also provided a washing machine including: a cabinet; a tub installed in the cabinet and storing washing water; a drum rotatably disposed inside the tub and washing and dewatering the laundry; a plurality of support springs mounted between an upper portion of the tub and an upper inner wall of the cabinet; and a plurality of dampers installed between a lower portion of the tub and a lower inner wall of the cabinet, wherein the damper includes: a cylinder connected with one of the tub and the cabinet; a piston rod disposed to be movable linearly in the cylinder and connected with the other of the tub and cabinet; a friction unit disposed to be movable in a radial direction inside the cylinder and generating a damping force by rubbing on an inner circumferential surface of the cylinder; and a damping force control unit mounted at the piston rod and controlling a damping force by moving the friction unit in the radial direction.

The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

In the drawings:

FIG. 1 is a sectional view of a general drum washing machine;

FIG. 2 is a sectional view of a damper for a washing machine in accordance with a conventional art;

FIG. 3 is a sectional view of a damper in accordance with the present invention;

FIG. 4 is an enlarged view of a portion ‘A’ of FIG. 3;

FIG. 5 is a perspective view of the friction unit of the damper in accordance with the present invention;

FIG. 6 is a front view of the friction unit of the damper in accordance with the present invention; and

FIGS. 7 and 8 illustrate operational states of the damper in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The drum washing machine in accordance with a preferred embodiment of the present invention will now be described with reference to the accompanying drawings.

FIG. 3 is a sectional view of a damper in accordance with the present invention, and FIG. 4 is an enlarged view of a portion ‘A’ of FIG. 3.

As shown in FIG. 1, the washing machine of the present invention includes: a cabinet 2 forming the exterior, a tub 4 disposed inside the cabinet 2 and storing washing water, a drum 6 rotatably disposed at the inner side of the tub 4 and washing and dewatering the laundry, a driving motor 10 positioned at a rear side of the tub 4 and rotating the drum 6 by being connected with the drum 6 by a driving shaft 8, a plurality of support springs 16 installed between an upper portion of the tub 4 and an upper inner wall of the cabinet; and a plurality of dampers 50 disposed between a lower portion of the tub 4 and a lower inner wall of the cabinet 2 and reducing transfer of vibration generated from the tub 4 to the cabinet 2.

The damper 50 includes a cylinder 52 mounted at one of an outer circumferential surface of the tub 4 and a bottom surface of the cabinet 2, a piston rod 54 mounted at the other of the outer circumferential surface of the tub 4 and the bottom surface of the cabinet 2 and disposed to be movable linearly inside th3 cylinder 52, a friction unit 56 disposed to be movable in a radial direction on an inner circumferential surface of the cylinder 52 and generating a damping force by rubbing on the inner circumferential surface of the cylinder 52, and a damping force control unit 58 mounted at the piston rod 54 and controlling a damping force by moving the friction unit in a radial direction.

One side of the cylinder 52 is opened to allow the piston rod 54 to pass therethrough, and a hinge connection part 60 which is connected with one of the tub 4 and the cabinet 2 is formed at the other side of the cylinder 52.

The piston rod 54 is disposed to be linearly and reciprocally movable on the inner circumferential surface of the cylinder 52, and a hinge connection part 62 which is connected with the other of the tub 4 and the cabinet 2 is formed at an end portion of the piston rod 54.

As shown in FIGS. 5 and 6, the friction unit 56 includes holders 70 disposed at equal intervals on an inner circumferential surface of the cylinder 52 and moved in a radial direction according to an operation of the damping force control unit 58, a friction member 72 mounted on an outer circumferential surface of the holders 70 and rubbing on the inner circumferential surface of the cylinder 52, and an elastic member 74 connected between the holders 70 and providing an elastic force in a direction that a diameter between holders is diminished.

The holders 70 are formed in an arc form and includes a sloped portion 76 slidably contacting with the damping force control unit formed at its inner circumferential surface and a fixing recess 78 formed at its outer circumferential surface, to which the friction member 72 is insertedly fixed.

The friction member 72 is formed as a circular ring type and its inner circumferential surface is insertedly fixed to the fixing recess 78 of the holders 70 and its outer circumferential surface rubs on the inner circumferential surface of the cylinder 52. The friction member 72 is made of a material whose diameter can be varied within a certain range, and preferably, made of a grease-absorbed sponge material.

The elastic member 74 is also formed as a circular ring type and formed as an elastic body made of a rubber material wound between the holders 70 and providing an elastic force in the direction that the diameter of the holders 70 is diminished.

The damping force control unit 58 includes an operating unit 80 disposed at an inner circumferential surface of the holders 70, expanding the holders 70 in the radial direction so that the friction member 72 can rub on the inner circumferential surface of the cylinder 52, and a driving force generating unit 82 mounted at an upper end of the piston rod 54 and generating a driving force for driving the operating unit 80.

The operating unit 80 includes a first operating member 84 fixed at an upper surface of the driving force generating unit 80 and a second operating member 86 mounted to be movable in a vertical direction on the first operating member 84. A sloped portion 88 is formed at at least one of facing surfaces of the first and second operating members 84 and 86 and contacts with the sloped portion 76 of the holder 70 to guide the holder 70 to be slidably moved.

A through hole 90 is formed at the center of the second operating member 86 and a fixing bolt 92 penetrates through the through hole 90. The fixing bolt 92 is engaged with the first operating member 84. Accordingly, the second operating member 86 is moved in the vertical direction within the interval (T) between the second operating member 86 itself and the head of the fixing bolt 92.

When the first and second operating members 84 and 86 are tightly attached, the sloped portions 88 form a V shape and the sloped portion 76 of the holder 70 contacts with the sloped portions 88. Accordingly, when the second operating member 86 is moved in the upward direction and spaced apart from the first operating member 84, the holder 70 is slidably moved in the direction that its diameter is diminished by the elastic force of the elastic member 74. Then, the friction member 72 is separated from the inner circumferential surface of the cylinder 52, so no damping force works. And then, when a driving force is generated from the driving force generating unit 82, the second operating member 86 is moved in the downward direction to be tightly attached with the upper surface of the first operating member 84 and the holder 70 is moved along the sloped portions 88 of the first and second operating members 84 and 86 and expanded in the radial direction. Then, the friction member 72 rubs on the inner circumferential surface of the cylinder 52 to generate a damping force.

Preferably, the first and second operating members 84 and 86 are formed as a magnetic material.

The driving force generating unit 82 includes a core 94 having a lower end fixed at the piston rod 54 and an upper end at which the first operating member 84 is integrally formed, and a coil 96 wound on an outer circumferential surface of the core 94 and generating a magnetic force by making the core 95 an electromagnet when power is applied thereto. Namely, when power is applied to the coil 96, the core 94 becomes the electromagnet to generate a magnetic force to pull the second operating member 86, namely, the magnetic material, in a downward direction.

The operation of the damper constructed as described above will now be explained.

FIGS. 7 and 8 illustrate operational states of the damper in accordance with the present invention.

First, when the drum 6 is rotated at a high speed RPM, power applied to the coil 96 is cut off to make a damping force zero. Namely, the holder 70 is moved in the direction that its diameter is diminished along the sloped portions 88 between the first and second operating members 84 and 86 according to the elastic force of the elastic member 74. Then, the friction member 72 is separated from the inner circumferential surface of the cylinder 52, generating no frictional force, so the damping force becomes zero.

When the drum 6 is rotated at a normal speed, movement of the second operating member 86 is controlled by adjusting strength of a current applied to the coil 96, according to which an amount of radial movement of the holder 70 is controlled to control the frictional force between the friction member 72 and the inner circumferential surface of the cylinder 52, thereby controlling the damping force.

If vibration is excessively generated at the drum, a current is applied to the coil 96 to make the core 94 and the first operating member 84 electromagnets to generate attraction with the second operating member, namely, the magnetic material, to pull the second operating member 86 in the downward direction. Then, the holder 70 is moved in the direction that its diameter is increased along the sloped portions 88 of the first and second operating members 84 and 86 to allow the friction member 72 to press the inner wall of the cylinder 52. Accordingly, the frictional force of the friction member 72 is increased to generate a strong damping force.

As so far described, the damper in accordance with the present invention has such an advantage that it can reduce vibration and noise of the washing machine by controlling the damping force by controlling a frictional force between the cylinder and the friction member by adjusting strength of a current applied to the coil.

As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalence of such metes and bounds are therefore intended to be embraced by the appended claims. 

1. A damper comprising: a cylinder; a piston rod disposed to be movable linearly in the cylinder; a friction unit disposed to be movable in a radial direction inside the cylinder and generating a damping force by rubbing on an inner circumferential surface of the cylinder; and a damping force control unit mounted at the piston rod and controlling a damping force by moving the friction unit in the radial direction.
 2. The damper of claim 1, wherein the friction unit comprises: holders disposed at equal intervals in a circumferential direction inside the cylinder; a friction member fixed at an outer circumferential surface of the holders and rubbed on the inner circumferential surface of the cylinder according to radial movement of the holders; and an elastic member connected between holders and providing an elastic force in a direction that a radius of the holders is diminished.
 3. The damper of claim 2, wherein the holder includes a sloped portion at its inner circumferential surface and a fixing recess to which the friction member is insertedly fixed.
 4. The damper of claim 3, wherein the friction member is made of a material which can be expanded and contracted in a radial direction within a certain range.
 5. The damper of claim 2, wherein the friction member is formed of a grease-absorbed sponge.
 6. The damper of claim 2, wherein the elastic member is formed as an elastic body made of a rubber material.
 7. The damper of claim 2, wherein the damping force control unit comprises: an operation unit disposed at an inner circumferential surface of the holders and pressing the holders so as to be expanded in a radial direction; and a driving force generating unit mounted at an upper end of the piston rod and driving the operating unit.
 8. The damper of claim 7, wherein the operating unit comprises: a first operating member fixed at the driving force generating unit; and a second operating member mounted to be movable in a vertical direction on the first operating member 84, and a sloped surface is formed at at least one of the first and second operating members and slidably contacts with the sloped portion of the holder.
 9. The damper of claim 8, wherein the first and second operating members are made of a magnetic material.
 10. The damper of claim 8, wherein the driving force generating unit comprises: a core formed at an upper surface of the piston rod and integrally formed with the first operating member; and a coil wound on an outer circumferential surface of the core and generating a magnetic force by making the core an electromagnet when power is applied thereto.
 11. A washing machine comprising: a cabinet; a tub installed in the cabinet and storing washing water; a drum rotatably disposed inside the tub and washing and dewatering the laundry; a plurality of support springs mounted between an upper portion of the tub and an upper inner wall of the cabinet; and a plurality of dampers installed between a lower portion of the tub and a lower inner wall of the cabinet, wherein the damper comprises: a cylinder connected with one of the tub and the cabinet; a piston rod disposed to be movable linearly in the cylinder and connected with the other of the tub and cabinet; a friction unit disposed to be movable in a radial direction inside the cylinder and generating a damping force by rubbing on an inner circumferential surface of the cylinder; and a damping force control unit mounted at the piston rod and controlling a damping force by moving the friction unit in the radial direction.
 12. The washing machine of claim 11, wherein the friction unit comprises: holders disposed at equal intervals in a circumferential direction inside the cylinder; a friction member fixed at an outer circumferential surface of the holders and rubbed on the inner circumferential surface of the cylinder according to radial movement of the holders; and an elastic member connected between holders and providing an elastic force in a direction that a radius of the holders is diminished.
 13. The washing machine of claim 12, wherein the holder includes a sloped portion at its inner circumferential surface and a fixing recess to which the friction member is insertedly fixed.
 14. The washing machine of claim 12, wherein the friction member is made of a material which can be expanded and contracted in a radial direction within a certain range.
 15. The washing machine of claim 12, wherein the friction member is formed of a grease-absorbed sponge.
 16. The washing machine of claim 12, wherein the elastic member is formed as an elastic body made of a rubber material.
 17. The washing machine of claim 12, wherein the damping force control unit comprises: an operation unit disposed at an inner circumferential surface of the holders and pressing the holders so as to be expanded in a radial direction; and a driving force generating unit mounted at an upper end of the piston rod and driving the operating unit.
 18. The washing machine of claim 17, wherein the operating unit comprises: a first operating member fixed at the driving force generating unit; and a second operating member mounted to be movable in a vertical direction on the first operating member 84, and a sloped surface is formed at at least one of the first and second operating members and slidably contacts with the sloped portion of the holder.
 19. The washing machine of claim 18, wherein the first and second operating members are made of a magnetic material.
 20. The washing machine of claim 18, wherein the driving force generating unit comprises: a core formed at an upper surface of the piston rod and integrally formed with the first operating member; and a coil wound on an outer circumferential surface of the core and generating a magnetic force by making the core an electromagnet when power is applied thereto. 